MEGAN THOMPSON: Every evening on the south side of the Hawaiian island of Kauai … just as the sun is about to set … a curious noise cuts through the tropical breeze. That’s the sound of parakeets.  Hundreds, perhaps thousands of parakeets. They come to the same tall royal palms and pine trees every night to sleep, before taking off at dawn to roam the island.

As the story goes, back in the 1960’s, a few rose-ringed parakeets were kept as pets at a local bed and breakfast.   They escaped, multiplied, and now there are an estimated 5,000 parakeets living here on Kauai. There’s something charming about these beautiful, bright green birds fluttering in the trees.  But it turns out, they’ve become quite a nuisance.

BILL LUCEY: It's the most complicated wildlife problem I've ever dealt with.

MEGAN THOMPSON: Bill Lucey is a biologist and the former manager of Kauai’s invasive species committee, which monitors the birds.

BILL LUCEY: What we're seeing is this, it's called a slow invasion. So they're around for a long time. And then they hit some sort of peak and they'll start breeding more rapidly. And the population, from what we're observing, is really startin' to grow fast.

MEGAN THOMPSON: Rose-ringed - or ring-necked - parakeets are native to parts of Africa and Asia and are often kept as pets. They have spread in the wild around the world, from Great Britain to Japan and now Hawaii. Kauai is known as the garden island because of its lush landscape and many farms, and that’s where the birds cause the most trouble.

Parakeets love the sweet tropical fruit grown on Kauai, like papaya, lychee and passion fruit. They can do a lot of damage in a short period of time.

JERRY ORNELLAS: You can see there’s some damage here

MEGAN THOMPSON: Jerry Ornellas grows lychee and other fruit on a 15-acre farm on Kauai’s east side.  

JERRY ORNELLAS: About four years ago we started seeing the first individuals. There were maybe two or three of them. And this year I'm seeing flocks of about 20 or 30.

MEGAN THOMPSON: Ornellas is retired and aims to break even with the farm, which has been in his family since the 60’s.  

JERRY ORNELLAS: Last year I lost about 30 percent of my crop which five or six thousand dollars loss on lychee.

JERRY ORNELLAS: Fact is I don't hate these birds. You know they're trying to make a living. Just like I am. And times are tough. I know for them as well as the farmers. But let me put it this way. How would you feel if Friday came along and you checked out your paycheck and birds and eaten half of your paycheck. I mean that's basically what we're looking at as farmers.

MEGAN THOMPSON: Farmer Gary Ueunten has started experimenting with ways to keep the birds off his lychee trees.

GARY UENTEN: I read on the internet that. In japan they use waxed paper bags to cover fruit. So I ordered a whole bunch of bags they started covering fruit. It worked for a little while. And then the birds figured out where we can eat right through the bag. So that was end of the bags.

MEGAN THOMPSON: Now Ueunten is putting huge nets over his trees to keep the birds away.  He figures he’s spent about $1200 so far.

GARY UENTEN: Oh yeah that's a huge expense for a small farmer to go out and spend 1200 dollars. It's a big expense.

MEGAN THOMPSON: On Kauai’s west side, some of the largest agricultural companies in the world are also battling the birds in the fields where they develop genetically modified corn seed.  

PETER WIEDERODER: That’s the first sign we see. When we see that, we know we need to move into action right away

MEGAN THOMPSON: These massive nets are stretched across a field owned by Dow Agrosciences. Peter Wiederoder works for Dow and is a member of the Hawaii Crop Improvement Association, which represents Dow, Monsanto, Dupont, Pioneer and Syngenta.  

PETER WIEDERODER: The difference between the parakeets and the other animals, is the parakeets have that ability to totally wipe out the entire field in a short time period.  Our scouts came in on a Friday-- to check the field out. The field was looking great, in good condition. We came back on Monday and every ear of corn had been totally eaten. It was down to just the cob.

MEGAN THOMPSON: The companies also hire people to scare the birds away. Wiederoder estimates all of it costs the four seed companies hundreds of thousands of dollars a year.

PETER WIEDERODER: This is one more thing that increases our price, and makes it less and less attractive for us to be here-- in Hawaii

MEGAN THOMPSON: Bill Lucey says the birds are hard to control because they’re so smart. They seem to be able to recognize farmers who’ve threatened them before.

BILL LUCEY: They recognize their jackets, the trucks they drive. What they'll do is send in two birds to scout the fields. They'll look for danger. If they see someone else's truck, that doesn't mean they're gonna fly away. But if they see a certain truck and they recognize it, they'll give out an alarm call. And the birds won't come in.

MEGAN THOMPSON: Wow.

BILL LUCEY: So people are changing their baseball hat colors. And changing their clothing.

MEGAN THOMPSON: They're literally in disguise.

BILL LUCEY: Yeah.

MEGAN THOMPSON: Wow.

BILL LUCEY: ‘Cause these birds are, I mean, you could teach parakeets and parrots to talk.

MEGAN THOMPSON: The parakeets aren’t just destroying farms.  

JACK BARNARD: We have droppings on our walkway all the way back through here.

MEGAN THOMPSON: The noise - and the big mess they make - are nuisances for tourists and residents who live beneath those trees they return to sleep in every night. And the local authorities suspect they might be stripping seeds from native plants in Kauai’s mountains, like the Koa tree.

And that gets to a larger issue facing the state of Hawaii. It’s one of the most isolated island chains in the world.  And that means native plants and animals here didn’t evolve to compete with foreign threats.

JOSH ATWOOD: When species from other parts of the world come to Hawaii, they tend to be much more competitive than some of the native species. And that delicate unique balance we have-- here in Hawaii can be upset really easily.

MEGAN THOMPSON: Joshua Atwood is the invasive species coordinator for Hawaii’s Department of Land and Natural Resources. The state spends about $57 million a year battling invasive plants, animals and insects, like the ornamental plant Miconia that now threatens Hawaii’s forests … the coffee berry borer that damages coffee plants…and invasive algae that smother coral reefs.

JOSH ATWOOD: The invasion of Hawaii by invasive species is the single greatest threat to not only Hawaii's natural resources, but to its economy, agriculture, and to the health and lifestyle of Hawaii's people.

MEGAN THOMPSON: Last spring, the Hawaii state legislature allocated $75,000 to start to figure out what to do about the parakeets on Kauai. Bill Lucey says if they can catch the birds, they could sell them to pet stores.

BILL LUCEY: One option is to stretch nets-- off the top so the buildings where the parakeets are roosting. And then we could catch them live. There's another option which has been used in the past. When the birds are sleeping, you can soak the tree with soapy water and they can't fly. So they'll fall down.

MEGAN THOMPSON: But Lucey says if catching them isn’t enough, the state may have to resort to killing the birds.  And that does not sit well with Cathy Goeggel, President of Animal Rights Hawaii, she objects to the idea the parakeets are invasive.

CATHY GOEGGEL: These birds have been here for 50 years. They are an established population. They are loved by a lot of people and I think it's kind of pie in the sky to think that they can trap them and then send them back into the pet trade where they'll probably go someplace else where they're not wanted.

MEGAN THOMPSON: Goeggel says, in no circumstances should they be killed. She’d prefer the state look at ways to slip birth control into their food, a technique used on pigeons in other parts of the US.

CATHY GOEGGEL: They are not responsible for having come to Hawaii on their own. They were brought here as a pet trade and released. And to kill them just because they're not native doesn't seem fair to me.

BILL LUCEY: You know, humane treatment of animals, we're all about that. But as resource managers, we look at the system. We don't look at the individual animal. We look at the ecosystem and how it functions. Is it healthy? Is it productive? Is it making space for all the native species?

MEGAN THOMPSON: And so until the authorities figure something out the residents of the south side of Kauai will fall asleep and wake up to this bird song for months, or maybe years, to come.